Exemplary embodiments of the present invention relate to a projector.
The related art includes a projector, a so-called 3-LDC projector to split a luminous flux output from a light source unit into color lights of three colors of red, green and blue by a dichroic mirror, to modulate them with respect to each color light in response to image information by three liquid crystal panels (light modulators), to combine the modulated luminous fluxes by a cross dichroic prism, and to enlarge and project a color image via a projection lens.
The related art projector has an illumination optical device 100 as shown in FIG. 9. This illumination optical device 100 has a light source unit 110 and a uniform illumination optical system 150.
The light source unit 110 has an arc tube 12 as a light emitting source, an ellipsoidal reflector 130, and a collimator lens 140. Accordingly, the radial light emitted from the arc tube 12 is reflected by the ellipsoidal reflector 130 and output, and collimated by the collimator lens 140.
The uniform illumination optical system 150 has a luminous flux splitting optical element (first lens array 160), a polarization changer element (PBS array 180), a second lens array 170, and a superposing lens 190. See related art document 1. Accordingly, the system is arranged to split the luminous flux reflected by the ellipsoidal reflector 130 into plural partial luminous fluxes and superpose them on the image forming region of a liquid crystal panel 41.
In such an illumination optical device 100, in order to take in all of the luminous fluxes from the arc tube 12, the outline shapes of the effective luminous flux transmitting regions of the first lens array 160, the second lens array 170, the PBS array 180, and the condenser lens 190, are formed in squares. Further, the side dimensions thereof are made nearly equal to the dimension of the diameter of the reflecting surface in the aperture of the ellipsoidal reflector 130 (hereinafter, referred to as “effective reflecting surface diameter”). Note that the “effective luminous flux transmitting region” is a region in which, of the luminous fluxes respectively passing through these optical components, the luminous flux that can pass through the image forming region (illuminated region) of the light modulator exists. For example, in the vicinity of the second lens array 170, the PBS array 180, and the condenser lens 190, condensed images (arc images) of the plural partial luminous fluxes split by the first lens array 160 are observed, and the effective luminous flux transmitting region in this case is a hypothetical rectangular region that includes these condensed images. Further, in order to enter all of the fluxes output from the collimator lens 140, the first lens array 160, the second lens array 170, the PBS array 180, and the superposing lens 190 arranged at the downstream side of the collimator lens 140 along the optical path, have effective luminous flux transmitting regions of squares having side dimensions thereof equal to that of the collimator lens 140.
On the other hand, the image forming region of the liquid crystal panel 41 is in a rectangular shape formed by significantly shorter short sides and long sides than the dimension of the diameter of the reflecting surface in the aperture of the ellipsoidal reflector 130. Accordingly, a large dimensional difference is produced between the side dimension of the effective luminous flux transmitting region of the superposing lens 190 and the dimensions of the short side and the long side of the image forming region of the liquid crystal panel 41, and the incident angle of the light output from the periphery of the superposing lens 190 to the liquid crystal panel 41 becomes larger. Since the liquid crystal panel 41 is normally designed so that the luminous flux that has been made into a collimated luminous flux by the ellipsoidal reflector 130, a lens, or the like, may enter the image forming region nearly perpendicularly. If the incident angle of the luminous flux becomes larger and the luminous flux enters the image forming region diagonally, the contrast of the projected image is easily deteriorated and the image quality can be degraded.
Further, there is a problem that further miniaturization of the illumination optical device 100 can not be addressed and/or achieved because the side dimensions of the effective luminous flux transmitting regions of the first lens array 160, the second lens array 170, the PBS array 180, and the superposing lens 190 are made nearly equal to the dimension of the diameter of the reflecting surface in the aperture of the ellipsoidal reflector 130 in order to take in all of the luminous fluxes from the arc tube 12.